Climate Change Scenario Analysis for Baro-Akobo River Basin, Southwestern Ethiopia

Muleta Environ Syst Res (2021) 10:24 https://doi.org/10.1186/s40068-021-00225-5 RESEARCH Open Access Climate change scenario analysis for Baro‑Akobo river basin, Southwestern Ethiopia Teressa Negassa Muleta* Abstract Background: Several water resources projects are under planning and implementation in the Baro-Akobo basin. Cur- rently, the planning and management of these projects is relied on historical data. So far, hardly any study has addressed water resources management and adaptation measures in the face of changing water balances due to climate change in the basin. The main bottleneck to this has been lack of future climate change scenario base data over the basin. The current study is aimed at developing future climate change scenario for the basin. To this end, Regional Climate Model (RCM) downscaled data for A1B emission scenario was employed and bias corrected at basin level using observed data. Future climate change scenario was developed using the bias corrected RCM output data with the basic objective of producing baseline data for sustainable water resources development and management in the basin. Result: The projected future climate shows an increasing trend for both maximum and minimum temperatures; however, for the case of precipitation it does not manifest a systematic increasing or decreasing trend in the next century. The projected mean annual temperature increases from the baseline period by an amount of 1 °C and 3.5 °C respectively, in 2040s and 2090s. Similarly, evapotranspiration has been found to increase to an extent of 25% over the basin. The precipitation is predicted to experience a mean annual decrease of 1.8% in 2040s and an increase of 1.8% in 2090s over the basin for the A1B emission scenario. Conclusion: The study resulted in a considerable future change in climatic variables (temperature, precipitation, and evapotranspiration) on the monthly and seasonal basis. These have an implication on hydrologic extremes-drought and fooding, and demands dynamic water resources management. Hence the study gives a valuable base informa- tion for water resources planning and managers, particularly for modeling reservoir infow-climate change relations, to adapt reservoir operation rules to the real-time changing climate. Keywords: A1B emission scenario, Baro-Akobo River Basin, Bias Correction, Climate change scenario, General circulation model, Regional climate model Background and infrastructures. Tis assumption is nowadays threat- Te planning and management of basin scale water ened by climate change and the notion that both climate resources systems has historically relied on assuming and hydrology will evolve in the future. Water resource stationary hydrologic conditions. Tis approach assumes planning based on the concept of a stationary climate is that past hydrologic conditions are sufcient to guide the increasingly considered inadequate for sustainable water future operation and planning of water resources systems resources management (Xueping et al. 2018; Mohamed 2015; Luca et al. 2020). According to the Series Assess- *Correspondence: [email protected] ment Reports of the Intergovernmental Panel on Climate Department of Sanitary and Environmental Engineering, Budapest Change (IPCC 2007) and many other studies, warming of University of Technology and Economics, Budapest, Hungary © The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. 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Muleta Environ Syst Res (2021) 10:24 Page 2 of 15 the climate system is unequivocal, as is now evident from downscaling approach in which a fne, at a much smaller observations of increases in global average air and ocean space-scale (e.g., 0.5° by 0.5°), computational grid over a temperatures, widespread melting of snow and ice, and limited domain is nested within the coarse grid of a GCM rising global average sea level (Myo and Zin 2020; Rah- (Wilby and Wigley 1997; Hewitson and Crane 1996; man 2018; Safeh et al. 2020; Jose et al. 2016). Cubash et al. 1996; Mearns et al. 1999). Adaptation is recognized as a critical response to the impacts of climate change. It can reduce pre- Climate and emission scenarios sent and future losses from climate variability and A climate scenario is a plausible representation of future enhance climate-resilient futures (Conde et al. 2011; climate that has been constructed for explicit use in inves- Cradock-Henr et al. 2018). It is a process that needs tigating the potential impacts of anthropogenic climate to be incorporated in the overall development plan- change (IPCC 2001). Te climate change scenarios should ning, including the design and implementation of be assessed according to consistency with global projec- water resources development. Over the last few tions, physical plausibility, applicability in impact assess- years, the literature on adaptation to climate change ments and representativeness (Hulme and Viner 1998). has expanded considerably worldwide: (Schneider Climate change scenarios are tightly dependent on the et al. 2000; Brekke et al. 2009; Li et al. 2010; Raje and emission scenarios. Future greenhouse gas (GHG) emis- Mujumdar 2010; Jones 1999). However, hardly few sions are the product of very complex dynamic systems, studies have addressed water management and adap- determined by driving forces such as demographic devel- tation measures in the face of changing water balances opment, socio-economic development, and technological due to climate change in Ethiopia. change (Luca et al. 2020). Scenarios are alternative images of how the future might unfold and are an appropriate tool Climate models and downscaling that assist in climate change analysis. According to IPCC General circulation models (GCMs) are tools designed Working Group III Special Report on Emission Scenario to simulate time series of climate variables globally, (SRES), four diferent narrative storylines were developed: accounting for efects of greenhouse gases in the atmos- (1) Te A1 storyline that describes a future world of very phere. Tey attempt to represent the physical processes in rapid economic growth, global population that peaks in the atmosphere, ocean, cryosphere, and land surface. Tey mid-century and declines thereafter and the rapid intro- are currently the most credible tools available for simulat- duction of new and more efcient technologies; (2) Te ing the response of the global climate system to increasing A2 storyline that describes a very heterogeneous world; greenhouse gas concentrations, and to provide estimates of (3) Te B1 storyline that describes a convergent world with climate variables (e.g., air temperature, precipitation, wind the same global population as in A1; and (4) Te B2 sto- speed, pressure, etc.) on a global scale. GCMs demonstrate ryline that describes a world in which the emphasis is on a signifcant skill at the continental and hemispheric spatial local solutions to economic, social, and environmental scales and incorporate a large proportion of the complexity sustainability. of the global system; they are, however, inherently unable to In the current study, the A1B storyline was chosen as it represent local sub grid-scale features and dynamics, which represents a balanced (moderate) future scenario in terms are of interest to a hydrologist (Myo and Zin 2020; Conde of the alternative energy, fossil intensive, socioeconomic, et al. 2011; Feyissa et al. 2018). and developmental trajectories. Te A1 scenario family Poor performances of GCMs at local and regional scales develops into three groups that describe alternative direc- have led to the development of limited area models (Dick- tions of technological change in the energy system as fos- inson et al. 1989; Dinckison and Rougher 1986; Anthes sil intensive (A1FI), non-fossil energy sources (A1T), or a et al. 1985). Tese techniques known as regionalization or balance across all sources (A1B). Even though it is true that downscaling are adopted in the literature to describe a set the occurrence of a single storyline is highly uncertain, the of techniques that relate the local and regional scale climate A1B scenario is adopted in this paper to have single-val- variables to the large scale atmospheric and oceanic forc- ued climate variable predictions instead of a ranged out- ing variables. Diferent regionalization techniques are avail- come from using ensemble of extreme trajectories. Tese able in the literatures so far: Spatial downscaling, Statistical projected climatic variables can, thus, directly be used for Downscaling, and Dynamic Downscaling (Barrow et al. climate change adaptation purposes like modeling climate 1996; Conway and Hulme 1996; Smith and Pitts 1997). change-runof relationships. For the current study, the dynamic downscaling method So far diferent studies have been conducted on the cli- (regional climate model version 3.1) was employed by mate change scenario development across the world using International Water Management Institute, Ethiopia, to diferent models and emission scenarios. Xueping et al. downscale the GCM output data at regional level. It is a (2018) with their study on Biliu River, China, has shown Muleta Environ Syst Res (2021) 10:24 Page 3 of 15 that climate emission scenarios are closely associated with in the north) has projected an increasing scenario both in temperature but not so closely associated with precipitation rainfall and temperature into the future (Roth et al. 2018). and runof; Conde et al.

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